1. Technical Field
The present invention relates generally to a method and apparatus for processing protocol packets and more particularly to a method and apparatus for processing MPEG media transport protocol packets.
2. Description of the Related Art
Moving Picture Experts Group (MPEG) Media Transport (MMT) is a standard technology developed by the ISO/IEC JTC1/SC29/WG11 System sub-working group from the year 2010. According to the ISO/IEC 23008-1 standard, an MMT system is composed of four functional areas chiefly classified into a Media Processing Unit (MPU) functional area, a delivery functional area, a signaling functional area, and a presentation functional area.
In ISO/IEC 23008-1 AMD.2, a header format for compressing the header of an MPEG Media Transport Protocol (MMTP) packet and operations related to compression is defined. In accordance with the ISO/IEC 23008-1 AMD.2, before an MMTP packet in which a header is compressed is transmitted, an MMTP packet having a full header is transmitted in conformity with a preset rule. Further, to process a compressed MMTP packet, the header information of an MMTP packet, which was transmitted prior to the compressed MMTP packet, is referred to. The header of the compressed MMTP packet includes a 5-bit Reference Sequence Number (RefSeqNum) field and an 8-bit reduced Sequence Number (reduced_SeqNum) field in order to indicate which MMTP packet is to be referred to when processing the corresponding packet. The RefSeqNum field may be set to the lower 5-bit value of the packet sequence number of the reference MMTP packet required to process the compressed MMTP packet. The reduced_SeqNum field may be set to the lower 8-bit value of the packet sequence number of each compressed MMTP packet.
Existing methods for searching for a reference MMTP packet utilize a 5-bit RefSeqNum field present in the header of a compressed MMTP packet. This MMTP packet has a packet sequence number that is a 16-bit value. An MPEG media transport receiving entity receiving entity detects an MMTP packet, the lower 5-bit value of the 16-bit packet sequence number of which is identical to the value set in the lower 5-bit position of the RefSeqNum field, and processes the header of the compressed MMTP packet using the value set in the header of the detected packet.
However, since the RefSeqNum field is set to the lower 5-bit value of the packet sequence number, there may be two MMTP packets, in which the lower 5 bits of packet sequence numbers are identical to each other. When there are two MMTP packets in which the lower 5 bits of the packet sequence numbers are identical to each other, the MPEG media transport receiving entity cannot determine which one of the two MMTP packets is to be referred to. Further, since the reduced_SeqNum field of the compressed MMTP packet has 8 bits, the MPEG media transport receiving entity cannot determine which one of two MMTP packets is to be referred to when the total number of a reference MMTP packet for a currently compressed MMTP packet and reference MMTP packets for subsequently compressed MMTP packets is a multiple of 256 (i.e., when the lower 8 bits of packet sequence numbers of two consecutive reference MMTP packets other than the compressed MMTP packets are identical to each other). Consequently, in the above-described cases, the MPEG media transport receiving entity cannot process the compressed MMTP packets.
Therefore, when there are two reference MMTP packets in which the lower 5 bits of packet sequence numbers are identical to each other, or even when the number of reference MMTP packets is a multiple of 256, a new MMTP packet processing method for allowing the MMTP packets to be correctly referred to is required.
Further, in addition to the problem with reference to MMTP packets, it may be inefficient to continuously transmit headers that include repetitive information when MMTP packets are frequently transmitted. Therefore, to solve the problem of repetitive transmission of headers, a method for compressing MMTP packets and processing the compressed MMTP packets is required.